With the popularization of large-screen handset, it becomes very convenient to perform single hand operations on large-screen handsets with single-hand mode user interfaces (UIs). There are two design manners for the three function keys of an Android system. In one manner, they are designed as virtual function keys within the screen. In the other manner, they are designed as physical function keys outside the screen. The virtual function keys within the screen will occupy some display area, while the physical function keys outside the screen do not affect the display interface on the screen.